It has been known that a cyclopropane compound such as (1R,2S)-1-(N-phenylmethylene)amino-2-vinylcyclopropanecarboxylic acid ester is useful as a production intermediate of pharmaceuticals such as an anti-hepatitis C agent [for example, see Organic Process Research & Development, vol. 14, pages 692 to 700, (2010)].
Concerning a method for producing a cyclopropane compound, a method of reacting N-phenylmethylene glycine ester with (E)-1,4-dibromo-2-butene in the presence of a N-benzylcinchonidinium compound and sodium hydroxide to obtain (1R,2S)-1-(N-phenylmethylene)amino-2-vinylcyclopropanecarboxylic acid ester is known in the above document. In the above-described method, 0.03 mol of a N-benzylcinchonidinium compound is used as an asymmetric catalyst, based on 1 mol of N-phenylmethylene glycine ester, and further, the reaction is carried out in the presence of sodium hydroxide.
The N-benzylcinchonidinium compound used as an asymmetric catalyst in the above method is not always satisfactory in stability under basic conditions. Therefore, when the N-benzylcinchonidinium compound is used in the reaction in the presence of sodium hydroxide, the N-benzylcinchonidinium compound sometimes decomposes during the reaction. In this case, there was a problem that a large amount of N-benzylcinchonidinium compound has to be used.
Therefore, the development of a new catalyst excellent in stability under basic conditions has been required.